It is generally known that physical exercise requires an increased and nutritionally adequate liquid intake. Dehydration rapidly decreases the capacity of an individual, but in hard training and competition the administration of salts and carbohydrates is also required in order to maintain the fluid balance, a proper salt balance and the energy level.
There is on the market today a large number of fluid and/or energy providing beverages. So called sports drinks are normally intended to be taken directly during the physical exercise to meet with the loss of fluids and salts of the body. A sports drink can be hypotonic, that is have a lower content of salts and sugars than the human body fluid, which means that it is quickly taken up by the body. Such a beverage is well fitted for short training sessions. An isotonic sports drink, that is having about the same concentration of salts and sugars as the human body, may well be used during harder and longer training sessions. A conventional sports drink contains in addition to water, carbohydrates, such as different sugars, in an amount of 4-8%, salts and minerals.
There are also different types of nutritional additives based on vitamins, minerals and other antioxidants, or in other ways stimulating substances such as caffeine or ginseng, which can either be provided in a sports drink or in the shape of tablets or powder or any other conventional form such as an energy cake.
In connection with physical exercise it is now generally believed that there is also an increased demand of proteins and many nutritional additive products therefore also contains one or more amino acids or proteins. This is especially true for products, which are used by body-builders and other strength sports performers.
When practising an endurance sport or exercising physically during a long period of time the body will be in a state of stress. This implies an increased flow of blood to the muscles, increased production of free radicals, and increased level of the so called stress hormones adrenaline, noradrenaline and cortisol. This state of stress also leads to gastrointestinal problems for many people practising said sports, such as marathon runners and hard training athletes. The gastro-intestinal problems can be manifested in many different ways, such as constipation, diarrhea, stomach ache, cramp or nausea (Nancy Rehrer et al., Gastrointestinal complaints in relation to dietary intake in triathletes, International Journal of Sport Nutrition, 1992, 2, 48-59). Competitive long-distance running is also said to induce gastrointestinal blood loss which may contribute to iron deficiency, runner's anaemia (James G. Stewart et al., Gastrointestinal Blood Loss and Anaemia in Runners, Annals of Internal Medicine, 1984, Vol. 100, No. 6, 843-845). Said intestinal bleedings might be due to a weakened intestinal mucosa.